Magnetic helix non-contacting linear drive

ABSTRACT

A non-contacting linear drive includes a fixed guidance part constructed as a profile part whose magnetic material in the vicinity of helixes (3,4) approaches (8,11,17) the latter and, at a distance from the helixes, forms a return path to the next helix. The rotary part has spaced double helixes, (3,4), a constant magnetic field (7) being produced in the magnetic circuit formed by a double helix and the magnetic return path. A very simple and economic construction and manufacture are consequently possible. The guidance part (2) can be constructed as a profile rail (9) or as a tube (10,15) and has window-like recesses (6), corrugations (11,12) or ribs (17). The double helix (1) can be constructed with permanent magnets (14) placed in the helixes with radial orientation or with permanent magnets (14) provided between soft magnetic helixes in axial orientation.

The present invention relates to a non-contacting or contact-free lineardrive according to the preamble of claim 1 and such as is e.g. used fordriving magnetic suspended railways and elevators.

Such a linear drive is known from DE-OS 31 20 28 and at present severalnon-contacting linear drive systems are known.

For example, a so-called linear motor is known, in which the stator isprovided along the guideway or track, while the rotor is located on thevehicle. Another known system has permanent magnets along the guidewayor track, while the vehicle carries an electromagnet, which continuouslychanges its polarity, so that it is drawn along the permanent magnets.

All these known drive systems suffer from the disadvantage that theyconsume a large amount of electric current, particularly because thereis a relatively large air gap between stator and rotor. However, thepower consumption increases with the square of the distance and inaddition a relatively large amount of energy is lost through heatgeneration.

DE-OS 31 20 328 discloses a linear motor whose primary part is a rotarycylindrical roller, on whose circumference are helically providedmagnets. The north and south poles are constructed as continuous bandsor strips and as a result in the vicinity of the cylinder surface isformed an axially travelling field. Due to the close succession of themagnetic pole strips, said field in part briefly closes between thepoles and only a relatively small part closes over the secondary part,in which is also produced a relatively high eddy current proportion.Therefore this known motor is not very economic.

In addition, German Patent 34 28 684 discloses a magnetic gear whoseprimary part is constructed as a magnet wheel, which cooperates with asecondary part slotted in tooth-like manner. This magnetic constructionalso has relatively low efficiency because the magnetic circuit is onlyclosed over the secondary part by two successive poles on the wheelcircumference.

SUMMARY OF THE INVENTION

The problem of the present invention is to provide a non-contactinglinear drive which has a very economic construction and operation. Thisproblem is solved by a non-contacting linear drive which includes atleast one linearly oriented, tubular fixed guidance part offerromagnetic material. Ferromagnetic double helixes are provided on theinner wall surface of the guidance part. The guidance part is a profilepart. At least one rotatable transportation part including a permanentmagnet is movable along the guidance part and is arranged coaxiallytherewith. Each helix of the guidance part corresponds to a pole of themagnet of the at least one transportation part. The rotatabletransportation part also has double helixes of ferromagnetic materialwhich are arranged around a core. A magnetic circuit is formed by theguidance part and the transportation part for producing a constantmagnetic field. The permanent magnets in the transportation part aremounted in such a way that the two helixes of the transportation partare oppositely polarized.

The construction of the operationally essential parts as a profile partand a double helix is relatively simple and leads to an inexpensiveconstruction.

According to a further development of the inventive concept, either thedouble helix can be the fixed guidance part and the rail the movabletransportation part or vice versa. When the invention is used forvehicles, e.g. magnetic suspended railways, it is appropriate to use theprofile rail as the fixed guidance part and the double helix as themovable transportation part. The rail can simultaneously form part ofthe suspended railway, while the double helix is fixed to the vehicle.

According to a further development of the inventive concept the profilepart can be differently constructed. It is important that in the sameaxial distance sequence as for the helixes, the profile part always doesor does not have material in the vicinity of the helix (rhythm: materialyes-no-helix-yes-no-helix, etc.).

Thus, the profile part can be a profile rail extending substantiallytangentially to the worm. However, the rail can also be curved about thesame axis as the worm and then substantially concentrically surrounds orencases at least in part the screw. This leads to a greater effectivearea and therefore to a higher efficiency.

Finally, the profile part can surround the screw as a concentric tubeand only a continuous, axial gap remains open through which project themounting or fixing elements for the screw.

Either when constructed as a rail, or when constructed as a tube, theprofile part can realize the material approach in different ways. Thus,the profile part can have window-like recesses, which are located overthe helixes and the magnetic flux takes place over the intermediatewebs.

The profile part can also have a substantially wavy or undulatoryprofiling with succeeding wave hills and valleys in the transportationdirection. It is advantageous if the tips of the wave hills close to thehelixes are substantially parallel to the circumferential surface andare substantially removed at the same axial extension of the helixes, sothat the magnetic flux is optimized.

Finally, the profile part can have ribs directed substantially at rightangles to the double helix, so that the base of a rib faces a helix withonly a limited spacing or gap.

The ribs can be applied or welded to a smooth support part. The profilepart can also comprise individual L-profile elements and in each casethe axially directed legs can e.g. be welded together as bodies and thelegs at right angles thereto are directed substantially radially withrespect to the worm. Finally, the profile part can be formed fromindividual U-profile elements, whose legs are superimposed in axialsequence, or from T-profile arranged with the central leg pointingradially inwards. This welded construction or production of the ribbedprofile part is particularly advantageous and economic in the case of atubular construction of the profile part.

Obviously the wavy profile part can also be welded together fromindividual elements or components, or the profile tubes can in each casebe constructed as welded endless tubes from L or U-profile stripmaterial.

According to another further development of the inventive concept themagnetic field acting between the two parts is produced by means ofpermanent magnets. The permanent magnets can be arranged either in thedouble helix or in the rail.

When the permanent magnets are arranged in the double helix, in a firstembodiment the construction is such that the two helixes are arrangedaround a soft magnetic core and the helixes are oppositely polarized.For this purpose, the magnets in the helixes with radial orientation areprovided in such a way that in one helix the south poles and in theother helix the north poles are always directed outwards. Thus, it ispossible to refer to a south pole helix and a north pole helix. Themagnetic flux resulting from this arrangement is as follows whenconstructing the profile part as a soft magnetic profile rail withrecesses. It comes out of the north pole, clears the air gap between theworm and the iron rail, then passes into a spoke of the profile rail andcomes out again before the next recess. It then clears the next air gapand enters the south pole of the next helix. The inner poles of thehelixes close through the soft magnetic core and consequently thecomplete circuit is closed. The helixes have a predetermined spacingfrom the iron rail. According to the invention, they can be rotated byan electric motor and according to a preferred embodiment are mounted onthe vehicle. The rotation of the helixes leads to a constant magneticfield, which moves the vehicle. Since, in this embodiment, the profilerail is fixed to the track or in the case of magnetic suspended railwaysis fixed to the support profile, the helixes in each case forming a wormare screwed thereto and along the same and consequently produce thenecessary drive for the vehicle on which the worms are fixed.

According to a second worm construction, the helixes can be made from asoft magnetic material, whilst the core is of a non-magnetic material.The permanent magnets are arranged in the gap between the helixes with asubstantially axial orientation. The magnets of one gap are introducedwith e.g. the north pole pointing in the transportation direction, whilethe other gap is equipped with south-oriented magnets, so that in eachcase a helix is flanked by identical poles, i.e. in each case a southhelix of south poles. Thus, in the helixes, there is a highconcentration of magnetic lines, so that the efficiency can be greatlyincreased.

According to a further development of the inventive concept the entiredouble helix can be made from a soft magnetic material, while thepermanent magnets in the profile rail are provided with the same spacingas the helixes of the double helix. The rotating double helixes overwhich closes the magnetic flux of the permanent magnets successivelyarranged in the transportation direction, lead to a drawing of thedouble helix worms along the magnet-equipped profile rails.

The inventive drive can be constructed in different ways, in thatdifferent numbers of double helixes and profile rails are associatedwith one another.

Thus, a single double helix can cooperate with a single profile rail.However, this is not the optimum case because the force ratio isrelatively one-sided, i.e. there is no force balance. Additionalprecautions must be taken, so that the spacing between the profile railand the helix is always maintained in an optimum manner.

There can also be two oppositely synchronously rotating double helixesand only one rail arranged between them. This constitutes a veryadvantageous embodiment, which has a multiplicity of uses.

A very good and precise operation is also provided by the constructionwith a double helix provided between two parallel profile railsdiagonally facing with respect to the double helix.

The transportation movement brought about by the linear drive cancontinuously take place in one direction, if e.g. the double helixes arecontinuously rotated in one direction. However, a reciprocating movementcan also be produced of the type particularly used in machine toolconstruction, if the helixes or the worm performs pivoting movements inthe clockwise or counterclockwise direction.

The worms formed from the helixes and the core can, e.g. be made torotate by means of an electric motor in per se known manner. However, itis also possible to transfer a rotary movement via known transmissionelements to the worm from other rotating components, e.g. of the vehicleor machine tool.

In the arrangement with two worms and one profile rail, the worms are soreciprocally arranged that in the case of their synchronous rotarymovement the helixes with the same poles always face one another inmirror symmetrical manner. As a result of the repulsion caused, agreater force is produced.

It is finally advantageous to provide on the double helix transportationpart a safety helix made from non-magnetic steel. This is a passivehelix, which need have no more than one or a maximum of two turns. Thesafety helix projects radially and relatively deep into the profile partand cooperates with its radial ribs in the manner of a friction brake.Thus, in the case of overloading of the rotor, the latter cannot slidethrough, because the safety helixes are mounted on the ribs of theprofile part and brake the sliding-through movement. The distancebetween the profile ribs and the safety helix must be such that, bymeans of the safety helix, the rotor is engaged on the profile ribsshortly before the magnetic field is interrupted or broken. This is thecase with an approximately 90% loading.

It is advantageous in the construction with double helixes and radiallyoriented magnets and at the same time space-saving to provide the safetyhelixes between the magnetic helixes on the core. In the case of axiallyoriented magnets this is not possible. It is then appropriate to providethe safety helixes on a core portion outside the pole helixes. Greaterstrength is obtained if in this area the core diameter is matched to thelarger diameter of the pole helixes, so that the safety helixessentially only has the height of the profile ribs.

The inventive drive has major advantages compared with the conventionallinear motor. The worms can be driven by a normal electric motoroperating in the ideal case, i.e. when the rotor and stator have thesmallest possible gap. The power consumption is always constant and isnot dependent on the size of an air gap.

The optimum and very economic usability of the inventive linear motor isalso very advantageous because the motor can be used for transportationmovements in substantially any random direction. Thus, it can be used inoptimum manner for horizontal transportation such as, e.g. for suspendedrailways, gates, machine tools or other machines where relativemovements have to be carried out of or within the complete machines.

It is also very advantageous to use the inventive motor for verticaltransportation, because compared with lifts or elevators for people orgoods operating in conventional manner with transportation cables, thereis no need for additional structures above and below ground for drives.Thus, there are no heavy cables or ropes e.g. for underground working itbeing possible to traverse galleries of great depth, whereas at presentit is necessary to travel along several reciprocally displaced sectionsinvolving in each case a new, complete transportation system with allthe resulting costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative tonon-limitative embodiments and the attached drawings: The drawings showin

FIG. 1 an inventive linear drive in a first embodiment with two doublehelixes and a profile rail as the profile part in plan view.

FIG. 2 a drive according to FIG. 1 in a second construction with adouble helix and two profile rails in plan view.

FIG. 3 a section along lines III--III of FIG. 1.

FIG. 4 a section along lines IV--IV of FIG. 2.

FIG. 5 a view along arrow V of FIG. 2 of a profile rail.

FIG. 6 a third construction of a linear drive with a double helix and anundulatory tube as the profile part.

FIG. 7 a section VII--VII of FIG. 6 showing the arrangement of themagnets in the helixes.

FIG. 8 a double helix in a further embodiment with soft magnetic helixesand interposed axially oriented magnets.

FIG. 9 a part section through a linear drive in another constructionwith a double helix according to FIG. 8 and formed from L-profile parts.

FIG. 10 a partial section through a linear drive in another embodimentwith a double helix with radially oriented magnets, a ribbed profiletube part assembled from U-profile parts and a safety helix.

FIG. 11 a section as in FIG. 10, but with a tube part with axiallyaligned magnets.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to FIG. 1, a non-contacting linear drive according to a firstembodiment comprises a profile part 2 constructed as a soft magneticprofile rail 9 with respect to each of whose flat sides is equidistantlyarranged, with an air gap, in each case one double helix 1 with the sameheight, i.e. in a substantially homologous manner. The double helix 1forming a worm essentially comprises a soft magnetic core 5 around whichare equidistantly arranged two helixes 3,4 made from permanent magneticmaterial or constituted by permanent magnetic pieces. The polarity issuch that it is oppositely directed from one helix to the next, so thata north helix 3 and a south helix 4 are formed. Thus, along the profileiron rail 9, considered in the longitudinal direction, a north pole anda south pole constantly alternate.

In a first embodiment, helixes 3 and 4 can be completely made from asoft magnetic material, but the possibility also exists of embeddingsmall bar magnets in radial alignment in non-magnetic material in such away that a double helix with a soft magnetic core is formed. Thisembedding can be brought about by using various known processes, such asby casting or sintering in.

The two helixes 1 in each case forming a worm are so arranged withrespect to one another and to the profile rail 9 that they are preciselymirror symmetrical to the rail, so that in each case a north helix ofone worm faces a north helix of the other worm at precisely the sameheight.

The iron rail has window-like recesses 6, which are longitudinallyarranged with the same reciprocal spacing as the helixes. The magneticflux formed by magnetic lines 7 is as follows. It comes out of the northpole, clears the air gap between the north helix 3 and the profile rail9 and then enters a spoke of rail 1. It then passes through spoke 8, soas to again clear the air gap between profile rail 9 and helix 4 at theheight of the latter and enters said south helix 4. The inner poles ofthe helixes close through the soft magnetic core 5.

In the embodiment shown in FIG. 2 the non-contacting linear drivecomprises a double helix 1, on whose two diametrically opposite sidesare arranged substantially homologously two profile rails 9. The profilerails also have recesses 6, which are substantially equidistant, so thatin each case a north helix faces a recess of the first profile rail andsimultaneously a south helix 4 faces a recess of the second rail 2.

FIG. 3 shows the symmetrical arrangement of two double helixes withrespect to a central rail (FIG. 1). It can be seen that the widthextension of profile 9 is substantially tangential to the outercircumference of in each case both double helixes and that the recess 6is precisely located between the helixes, namely between homopolarhelixes, in this case the north helixes 3. As a result of the rotarymovement, the helix circumference closest to the rail runs in thelongitudinal direction of the latter, e.g. upwards in FIG. 1. Thus, itis accompanied by the magnetic field which also runs through the rail.It has the tendency to make the rail also run. In the case of a fixedarrangement of the double helixes and the movable arrangement of therail, the latter will also perform this translatory movement. In thecase of a fixed arrangement of the iron rail and the fixing of thedouble helixes to a vehicle the helixes will also draw along the rail insuch a way that the optimum magnetic field 7 is maintained through thespokes 8 of the profile rail. In the same way, in the embodiment shownin FIG. 2, it is possible to produce the movement of the parts. Onceagain the magnetic field 7 closes in the same way as in FIG. 1, but oneither side of the double helix and substantially diagonally opposite tothe two helixes leading to the same movement type as in the embodimentaccording to FIG. 1. Either the iron rail is moved, or the helixes movealong the profile rails corresponding to the rotation direction.

FIG. 4 shows the symmetrical arrangement (as in FIG. 2) of the twoprofile rails 9 with respect to the double helix.

FIG. 5 is a view of a profile rail 9, it being possible to see therecesses 6 with the interposed spokes 8.

The embodiment of FIGS. 6 and 7 comprises a double helix 1, in whichpermanent magnets with a radial orientation are arranged in helixes 3,4.Core 5 is made from soft magnetic material. Around the double helix isprovided a substantially concentrically arranged, corrugated tube, whichin axial sequence has hills 11 and valleys 12. The corrugations or wavesare made with the same pitch and slope as the helixes 3,4 of doublehelix 1. The double helixes and corrugated tube are so associated withone another that in each case a helix faces a hill having a flattenedtip.

As can in particular be gathered from FIG. 7, tube 10 has a slot-like,axial opening 13, through which pass not shown mounting or fixingelements for double helix 1.

FIG. 8 shows a double helix, in which the helixes 3,4 are made from softmagnetic material and are wound around a non-magnetic core 5. Permanentmagnets are arranged in axial orientation in the gaps between helixes3,4 and as can in particular be gathered from FIG. 9. The permanentmagnets 14 are inserted with alternating polarity, so that in each casea gap with north orientation alternates with a gap having southorientation. Thus, a helix is always flanked by identical magneticpoles, which simultaneously leads to the polarity of the helixes. Thisleads to a very high concentration of magnetic lines 7, whichessentially have the configuration shown in broken line form in FIG. 9.

In the case of the embodiment shown in a relatively small detail in FIG.9, the profile part 2 is constructed as a ribbed tube 15. The radiallydirected ribs 17 are in each case part of a L-profile 16, which isjoined together to form an endless tube by welding. In the embodimentaccording to FIG. 10, the double helix is provided with radiallyoriented magnets 14, in the same way as in FIGS. 1, 2 and 6. Profilepart 2 is formed in the same way as in the embodiment of FIG. 9, usebeing made of U-profiles, which are welded together in axial sequencewith their legs resting on one another. The welded together legs in eachcase form a rib 17 of the thus produced profile part 2.

A safety helix 20 of non-magnetic steel is provided between the polehelixes 3, 4 of double helix 1 and can have one to two turns. Helix 20projects relatively far and in radially projecting manner between theribs 17 of profile part 2 or 15 and has on its braking area cooperatingwith ribs 17 a brake lining 21. Helix 20 is fixed to the substantiallyrod-like core 5 of soft magnetic material of the double helix 1, e.g. bywelding.

Finally, FIG. 11 shows another embodiment, in which the double helix 1is constructed in substantially the same way as in FIG. 8 and withaxially oriented magnets 14. As in FIG. 10, the profile part 2, 15 iswelded together from U-profiles. Once again a safety helix 20 isprovided, but is arranged outside the core portion with the pole helixes3, 4 of double helix 1. This can, e.g. be the rotor end. For thispurpose core 5 is provided with a step 22, which has a larger diameterand the latter roughly corresponds to the diameter of the pole helixes3, 4. The active braking area of the safety helix 20 is also providedwith a brake lining 21 which, in this embodiment, substantially coversthe entire active end face of the safety helix, whereas in theembodiment according to FIG. 10 the brake lining represents only part ofthe axially directed safety helix braking area. The safety helixes 20are in each case so spaced with respect to the ribs 17 that even in thecase of 90% of the maximum loading, the safety helixes 20 are engaged onribs 17 and braking starts without the magnetic fields being broken orinterrupted beforehand.

I claim:
 1. Non-contacting linear drive, includingat least one linearlyoriented, tubular fixed guidance part of ferromagnetic material, theguidance part having an inner wall surface, ferromagnetic double helixesbeing provided on the inner wall surface, the guidance part being aprofile part, at least one rotatable transportation part including apermanent magnet, the transportation part being movable along theguidance part and being arranged coaxially therewith, each helix of theguidance part corresponding to a pole of the magnet of the at least onetransportation part, the improvement comprising the rotatabletransportation part (1) also having double helixes (3, 4) offerromagnetic material, the double helixes (3, 4) of the transportationpart (1) being arranged around a core (5), a magnetic circuit beingformed by the guidance part and the transportation part producing aconstant magnetic field (7), and the permanent magnets (14) in thetransportation part (1) being mounted in such a way that the two helixes(3, 4) of the transportation part (1) are oppositely polarized. 2.Linear drive according to claim 1, wherein the guidance part (2) haswindow-like recesses (6), helical webs (8) being located axially betweenthe recesses (6) and having the same spacing as the helixes (3, 4) ofthe transportation part.
 3. Linear drive according to claim 1, whereinthe guidance part (2) has an undulatory profiling with hills (11) andvalleys (12) succeeding one another in transportation direction andwhich have the same spacing as the helixes (3, 4) of the transportationpart.
 4. Linear drive according to claim 1, wherein the guidance part(2) has ribs (17) substantially at right angles to the double helixes(3, 4) of the transportation part, the ribs (17) having the same spacingas the helixes (3, 4) of the transportation part.
 5. Linear driveaccording to claim 3, wherein the hills (11) have cut-off tips extrudingsubstantially parallel to the outer cylindrical circumferential surfaceof the helixes (3, 4) of the transportation part and over substantiallythe same axial extension as the helixes (3, 4) of the transportationpart.
 6. Linear drive according to claim 1, wherein the double helixes(11, 17) of the profile parts (2) are inclined in substantially the samedirection as the helixes (3, 4) of the transportation part.
 7. Lineardrive according to claim 4, wherein the ribs (17) of guidance part (2)each form one leg of L-profiles (16), each leg being connected to thesuccessive other leg by welding.
 8. Linear drive according to claim 4,wherein the ribs (17) of guidance part (2) are formed by flat-outsidesuperimposed legs of two U-profiles (18) succeeding one another in thetransportation direction and nondetachably interconnected.
 9. Lineardrive according to claim 7, wherein, when the guidance part (2) isconstructed as a ribbed tube (15), the L-profile 16 is constructed bywelding to form an endless tub with internal helix ribs (17).
 10. Lineardrive according to claim 1, wherein the magnets (14) are arranged inradial orientation in the helixes (3, 4) of the transportation part. 11.Linear drive according to claim 1, wherein the helixes (3, 4) of thetransportation part are made from soft magnetic material, core (5) ismade from non-magnetic material and the magnets (14) are arranged in agap defined between the helixes (3, 4) of the transportation part inaxial orientation.
 12. Linear drive according to claim 1, wherein atleast one safety helix (20) made from non-magnetic steel is arranged onthe double helix transportation part which has a maximum of two turnsand substantially extends over the entire extension of ribs (11,17) inthe tube profile part (10,16,18) and cooperates with said ribs (11, 17)of the profile part (10, 16, 18).
 13. Linear drive according to claim12, wherein the safety helix (20) is arranged between the pole helixes(3,4) with radially oriented magnets (14) on core (5).
 14. Linear driveaccording to claim 12, wherein in the case of axially oriented magnetsthe safety helix (20) is provided on a portion of core (5) locatedoutside the magnetic helix zone (3,4).
 15. Linear drive according toclaim 8, wherein, when the guidance part (2) is constructed as a ribtube (15), the U-profile (18) is constructed by welding to form anendless tube with internal helix ribs (17).